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  <div class="titlepage"><div><div><h1 style="clear: both"><code>BOOST_OUTCOME_CO_TRYV(expr)/BOOST_OUTCOME_CO_TRY(expr)</code></h1></div></div></div>
  <p>Evaluate from within a coroutine an expression which results in a type matching the following customisation points, continuing execution if successful, immediately returning <a href="../../reference/functions/try_operation_return_as.html" class="api-reference"><code>try_operation_return_as(X)</code></a>
 from the calling function if unsuccessful:</p>

<ul>
<li><code>BOOST_OUTCOME_V2_NAMESPACE::</code><a href="../../reference/functions/try_operation_has_value.html" class="api-reference"><code>try_operation_has_value(X)</code></a>
</li>
<li><code>BOOST_OUTCOME_V2_NAMESPACE::</code><a href="../../reference/functions/try_operation_return_as.html" class="api-reference"><code>try_operation_return_as(X)</code></a>
</li>
<li><code>BOOST_OUTCOME_V2_NAMESPACE::</code><a href="../../reference/functions/try_operation_extract_value.html" class="api-reference"><code>try_operation_extract_value(X)</code></a>
</li>
</ul>

<p>Default overloads for these customisation points are provided. See <a href="../../recipes/foreign-try.html">the recipe for supporting foreign input to <code>BOOST_OUTCOME_TRY</code></a>.</p>

<p>The difference between the <code>BOOST_OUTCOME_CO_TRYV(expr)</code> and <code>BOOST_OUTCOME_CO_TRY(expr)</code> editions is that the latter will set a variable if two or more macro arguments are present (see <a href="../../reference/macros/co_try.html" class="api-reference"><code>BOOST_OUTCOME_CO_TRY(var, expr)</code></a>
). The former requires the <code>T</code> to be <code>void</code>.</p>

<p>Hints are given to the compiler that the expression will be successful. If you expect failure, you should use <a href="../../reference/macros/co_tryv_failure_likely.html" class="api-reference"><code>BOOST_OUTCOME_CO_TRYV_FAILURE_LIKELY(expr)</code></a>
 instead.</p>

<p>An internal temporary to hold the value of the expression is created, which generally invokes a copy/move. <a href="../../tutorial/essential/result/try_ref.html">If you wish to never copy/move, you can tell this macro to create the internal temporary as a reference instead.</a></p>

<p><em>Overridable</em>: Not overridable.</p>

<p><em>Definition</em>: Firstly the expression&rsquo;s temporary is bound to a uniquely named, stack allocated, <code>auto &amp;&amp;</code>. If that reference&rsquo;s bound object&rsquo;s <code>try_operation_has_value()</code> is false, immediately execute <code>return try_operation_return_as(propagated unique reference);</code>, propagating the rvalue/lvalue/etc-ness of the original expression.</p>

<p><em>Header</em>: <code>&lt;boost/outcome/try.hpp&gt;</code></p>


        </div><p><small>Last revised: February 12, 2021 at 20:25:43 UTC</small></p>
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